The W.M. Keck Center for Cellular Imaging (KCCI), a leading center in advanced light microscopy imaging, particularly in protein-protein interaction imaging, is requesting a Zeiss "Multiphoton Spectral Imaging Microscopy (MSIM)" system. KCCI is a University wide imaging facility and the requested instrument will benefit the basic and clinical science investigators of this university, and in particular the 8 participating Federally funded investigators. The instrument will be housed in the well-established KCCI, located within walking distance of all the participating investigators. The central theme of the research to be performed on the requested Zeiss MSIM is the study of protein-protein interactions in live cells and tissues including: liganddependent protein interactions between ERalpha and corepressor proteins; mitochondria! disruption in traumatic axonal pathogenesis; FRET Imaging of Rho family GTPases; association of tau protein in Alzheimer's disease; the pattern of strain fibronectin networks during gastrulation; the dynamics of astroglial processes and their interactions with injured neurons; gene regulatory mechanisms in transgenic embryos; and cellular uptake of anti-cancer drugs. This system allows the application of biophysical techniques such as fluorescence recovery after photobleaching (FRAP), and fluorescence resonance energy transfer (FRET), to live specimens, in situ. Our request for the Zeiss MSIM is in response to the growing need of researchers at this institution to take advantage of these technological advances in their NIH-funded projects. KCCI is an internationally known center in the study of protein-protein interactions using various light microscopy techniques and provides hands on training annually for scientists from the United States as well as scientists from 15 countries. Currently, we do not have a multiphoton spectral imaging system, this is essential for our investigators, as well as for training others, to study the protein associations in living cells and tissues. In summary, the requested instrument will provide the research community at the University of Virginia with a level of imaging capability that has not been available in the past and will enhance ongoing and future research significantly.